Barnesville, the county seat for Lamar County, was incorporated February 20, 1854. The city was named for Gideon Barnes, who operated a log house tavern and a stage line between Macon and Columbus.

The Lamar County courthouse is listed on the National Register of Historic Place and was constructed in 1931.

Other historic sites in Barnesville are the Confederate Cemetery and the Gachet House. The Old Jail Museum, the former jail, features relics from the city’s history.